a. Field of the Invention
The present disclosure relates generally to an electromagnetic positioning sensor for a medical device, and more specifically to an electromagnetic positioning sensor that can sense roll.
b. Background Art
Medical devices such as guidewires, catheters, introducers and the like with electromagnetic coil position sensors for device navigation are used in various medical procedures in the body. For example, it is known to equip a catheter with multiple coils sufficient to allow a positioning sensor to detect six (6) degrees-of-freedom (DOF), namely, a three-dimensional (3D) position (X, Y, Z) and a 3D orientation (e.g., roll, pitch, yaw) thereof. However, the design of a coil assembly that can provide such functionality provides challenges, particularly with respect to space constraints.
One known electromagnetic position sensor includes a coil wound symmetrically on a tubular core. Such a sensor may be seen by reference to U.S. Pat. No. 7,197,354 entitled “System for Determining the Position and Orientation of a Catheter” issued to Sobe, hereby incorporated by reference in its entirety as though fully set forth herein. Sobe discloses a core that is hollow, symmetric about a central axis, and can be scaled in length, inner diameter, and outer diameter for a particular application. A coil is wound on the core in a desired winding pattern. The coil, like the core, is symmetric about the central axis. The sensor can detect three degrees of position (X, Y, and Z), as well as pitch and yaw, but the coil cannot detect roll (i.e., the rotational position with respect to the axis of the core). Accordingly, a medical device that incorporates a single symmetric sensor coil only senses five (5) DOF, that is, two orientation parameters, in addition to three position parameters. Despite the DOF limitation, there are nonetheless desirable aspects of the above configuration. For example, the configuration uses minimal space and accommodates an open central lumen.
Known solutions for sensing the roll of a medical device generally involve using multiple sensors, each with a single symmetric coil as described above. For example, both U.S. Patent Application Publication No. 2010/0324412, entitled “Catheter With Obliquely-Oriented Coils” and U.S. Pat. No. 6,593,884, entitled “Intrabody Navigation System for Medical Applications”, both of which are hereby incorporated by reference in their entireties as though fully set forth herein, teach placing separate sensors in different locations in a medical device with their respective coils oriented at different angles. Such configurations are more expensive and require more space in a medical device than a unitary sensor on a single core.
There is therefore a need for an electromagnetic position sensor that minimizes or eliminates one or more of the problems set forth above.